Seats of cars and trains, various sofas, office chairs and the like adopt a structure which covers a cushion body with a covering material, and which has a depression shape that satisfies ergonomic requirements such as the maintaining of seating posture and prevention of fatigue due to seating for a long time. In the seat and the like having such a depression shape, they employ a foamed body as a cushion body 111 which has fixed a surface fastener 110 onto the depressed shape portion, and the cushion body and the covering material are fixed by engagement between one surface fastener 110 integrated into the cushion body 111 and other surface fastener attached to the back surface of the covering material, in order to prevent the covering material from rising up from the cushion body in the depression shape portion, as shown in FIG. 11.
An example of producing the cushion body in which the surface fasteners are integrated into the surface is shown in FIG. 12. As shown in this figure, the cushion body which is a foam molded product integrated with the surface fasteners 122 is produced by placing the surfaces having the engaging elements of the surface fasteners 122 within a desired mold 121 so as to bring into contact with the mold surface, injecting a foam resin raw material within the mold 121, and foaming the foam resin raw material. The cushion body is often made of a polyurethane foam. As a method of fixing the surface fastener 122 on the mold surface, there has been known a method which comprises incorporating a magnetic material into a resin composition configuring the surface fastener, and fixing the surface fastener by attraction force between this magnetic material and magnets 123 placed within the mold 121.
It is known that the surface fastener used in such an application generally comprises a substrate portion in the form of flat plate and a plurality of engaging elements (in a shape of hook or loop) protruding from the substrate portion, and can be produced by integrally molding a thermoplastic resin composition.
Patent Document 1 (WO 2003/030672) proposes to incorporate a magnetic material into a substrate portion or engaging elements, and to integrally mold a surface fastener using a synthetic resin such as polyesters, polyamides, polyolefins, poly(vinyl chloride), polyurethanes, polyolefin-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyisoprene, or other resin compositions comprising a thermoplastic polymer(s). Further, Patent Document 1 discloses a method of extruding a synthetic resin containing magnetic powders and a synthetic resin containing no magnetic powders from each independent pathway within an extruder into molding cavities.
Patent Document 2 (U.S. Pat. No. 5,725,928) discloses that a surface fastener is produced by a substrate portion and engaging elements made of a mixture of a magnetic material and a non-magnetic material, and the non-magnetic material is made of a polypropylene, a polyethylene, a polyamide, a polyester, a polystyrene, polyvinyl chloride, acetal, an acrylate, a polycarbonate, poly(phenylene oxide), a polyurethane, polysulfone and a thermoplastic elastomer. It also discloses that the substrate portion and the engaging elements are molded by co-extrusion molding.
Patent Document 3 (Japanese Unexamined Utility Model Application Publication No. 4-40808) proposes a molded surface fastener in which at least a part of engaging elements or a substrate portion is made from a resin containing from 15 to 40% by volume mixing ratio of magnetic fine particles. It discloses, as the resin, thermoplastic resins such as polyesters, polyamides, polyolefins, poly(vinyl chloride), and polyurethanes. This document discloses that a decreased amount of magnetic material contained in the molded body of the molded surface fastener may result in lower magnetization force so that exact mounting is not possible, and an increased amount of magnetic material may result in a lower flexible property of the surface fastener so that its flexibility becomes poor.